Design Of The Alpha-Based Brain-Computer Interface System

Brain Computer Interface (BCI) is a direct information communication and control channel established between human and computer or other electronics devices and it is a wholly new communication system that does not depend on the brain's normal output pathways of peripheral nerves and muscles. A wide variety of neuromuscular disorders can disrupt the channels through which the brain communicates with and controls its external environment, usually deprive patients of their basic movement function and normal communication. Those most severely affected may be completely locked in to their bodies, unable to communicate with conventional assistive devices. As a wholly new information communication and control technology, EEG-based BCI may provide the paralyzed, especially those "locked-in" but with intact ideation, with an effective communication and control channels with outside world. That's why BCI is winning more and more attention. In terms of the fact that increase in the alpha component of EEG during eye closure exists among at least 90% of people with normal brain neural function, this dissertation presents a simple and easy alpha wave based BCI system. It requires only two electrodes to be placed towards the rear of the head for each person, can rapidly and highly reliably control a switch needless of training and it can further be extended to offer more sophisticated real time control. First, the lab Eye-Closure Based Activation System (ECBAS) is established. By providing with Switch Suppress Module(SSM)and sound feedback, a user can rapidly and reliably switch a single indicating light. Ten subjects attended ECBAS experiment by switch an indicating light continuously for 50 times. They have acquired the average error rate of 4% and average switch time of 2.4 seconds. This result indicates that the alpha amplitude variety with eye open and eye closure can be a rapid and reliable control for electronics switch. Next, on base of ECBAS, the Recycling Lights Choice Menus System (RLCMS) is developed and designed on the computer LabVIEW platform. It Extends ability of switching a light during eye closure to four options choice by a recycling light choice menu. Five subjects attended the experiment for RLCMS by continuously choosing demanded options for 20 times in four sections. All subjects have acquired an error rate of at least 10% after a short-term training. It is indicated that RLCMS is easy to learn and operate needless of extra biofeedback training and that the ECBAS is reliable enough to be extended to four options control from only two-state switch control. Last, with RLCMS as a prototype, the Minicar System Controlled by Alpha (MSCA) is designed to realize telecontrol minicar control by eye closure alpha wave. Five subjects attended continuous 25 times random command control experiment, and they have acquired average correction rate of 91.2%. By successfully realizing the real time control of outer device, it is proved that the RLCMS is feasible and with potential application value. With further development of integrated and portable system and suitable control panel, this alpha wave based BCI system could provide those locked-in but with intact mind with a new assistive product, such as control of a wheelchair.